Preheat oven to 375 F. Line a cookie sheet with parchment paper or silplat mat.
Combine dry ingredients: flour, cocoa powder, baking powder, baking soda and salt in medium bowl; set aside.
Combine wet ingredients: butter, sugar and brown sugar in a separate mixing bowl and beat for a few minutes until creamed together. Add egg and vanilla and mix until combined.
Add dry ingredients: Gradually mix in the flour mixture until combined. Stir in chocolate chips.
Refrigerate: Cover bowl and refrigerate dough for 30 minutes (or up to 3 days stored in an air-tight container).
Scoop dough: Measure out 1/4 cup balls of dough and place on baking sheet 2 inches apart.
Bake for 12 to 15 minutes or until set around the edges (don't over bake!).
Allow to cool for several minutes on the baking sheet before transferring to a wire rack to cool completely
Store leftover cookies in an airtight container at room temperature.
Make ahead Instructions: Make the dough up to 2 days ahead of time and store it in the refrigerator. Freezing Instructions: The cookie dough balls may be frozen for up to 3 months. To freeze the baked cookies, allow them to cool completely and store in a freezer-safe bag for up to 3 months.